(il) (A) NO. 1,122,309 (45) ISSUED 820420

(52) CLASS 341-100

3 (51) INT. CL. F22B 37/00,

F28G 15/00

(19) (CA) C A N A D I A N P A T E N T w

(54) METHOD FOR SERVICING A STEAM GENERATOR

(72) Cooper, Frank W., Jr.? Castner, Raymond P.,

U.S.A.

(73) Granted to Westinghouse Electric Corporation U.S.A

(21) APPLICATION No 337,276 (22) FILED 791010 (30) PRIORITY DATE U.S.A. (952,431) 781018

No. OF CLAIMS 9

DISTRIBUTED BY THE PATENT OFFICE, OTTAWA. CCA-274 (3-80)

-«T- W.E. 47,863 A b s t r a c t

A servicing machine for a steam generator is

accurately sel: up in the generator channel head with a

pivoted arm mounted for rotation in a plane parallel to the

tubesheet. The angular position of the arm, the

longitudinal position of a carriage mounted on the arm and

Che vertical position of a platform on the carriage are

remotely control loci to maneuver a probe used in mapping the

precise location ol" the thousands of holes in the

tubesheet. Various operations are then performed at each

precise hole location by tools carried by the arm mounted

carriage to prepare for Installation of new tubing. The

operation of a pair of remotely controlled pivoted arms,

one on each side of the channel head divider plate, is

coordinated to automatically position the ends of U-shaped

tubes in 'corresponding holes In the tubesheet on opposite

sides of the divider plate and to secure the same in place.

1122309

-1- W.E. 47,863 Method for Servicing a Steam Generator

Cross-Reference to Related Patent and Application This application is hereby cross-referenced to the

following commonly assigned Canadian patent and application: No. 1,090,991 issued on December 9, 1980 to

Lenard R. Golick and entitled "Apparatus for Remotely Repairing Tubes in a Steam Generator"; and

Canadian Application No. 336,549 filed on September 27, 1979 in the names of Kenneth S. Gerkey, Raymond P. Castner and Richard L. Stiller and entitled "Heat Exchanger Tube and Tubesheet Location Sensing Device and Method of Operation".

Background of the Invention Field of the Invention

This invention relates to a method and apparatus for servicing a steam generator and, more particularly, to

#

112:2309 -2- W.E. 47,863

a method and apparatus for remotely servicing the tubes and tubesheet of such a generator. Prior Art

In a boiling water nuclear powered electric generating system, the heat generated by the nuclear reaction is absorbed by a primary coolant that circulates through the reactor core and is utilized to generate steam in a steam generator. The steam generator typically is an upright cylindrical pressure vessel with hemispherical end

10 sections. A transverse plate called a tubesheet, located at the lower end of the cylindrical section, divides the steam generator into a primary side, which is the lower hemispherical section below the tubesheet, and a secondary side above the tubesheet. A vertical wall bisects the primary side into an inlet section and an outlet section. The tubesheet is a thick carbon steel plate with an array of thousands of holes into which are inserted the ends of U-shaped tubes. One end of each U-shaped tube is inserted into a hole in the tubesheet which communicates with the

20 inlet section of the primary side and the other end is inserted in a hole which communicates with the outlet section. The primary coolant is introduced under pressure into the inlet section of the primary side, circulates through the U-shaped tubes and exits through the outlet section. Water introduced into the secondary side of the steam generator circulates around the U-shaped tubes and is transformed into steam by heat given up by the primary coolant.

Occasionally during the operation of the steam 30 generator, leaks develop in some of the tubes. This is

112:2309 -3- W.E. 47,863

undesirable because the primary coolant is radioactive and any cross-feed of reactor coolant into the secondary side of the generator contaminates the steam. It is not practical, however, to replace leaky tubing as it occurs, but instead the steam generator is taken out of service temporarily and the affected tubes are plugged at both ends. In view of the thousands of tubes in the steam generator, plugging of a few does not appreciably affect the efficiency of heat transfer.

10 Eventually, however, a sufficient number of tubes may be plugged to adversely affect heat transfer and generator efficiency. More often, the steam generator is shut down for scheduled retubing of the entire unit. In the retubing process, all the tube holes, including any plugged holes, are drilled out and spot-faced from the primary side and the tubes are then pulled out from the secondary side. New tubes are inserted from the secondary side with tube guides inserted in the tube ends to ease their passage through holes in transverse support plates on the secondary

20 side and the appropriate holes in the inlet and outlet sides of the tubesheet. The tube guides are then removed from the primary side and the ends of the tubes are aligned with the spot-faced end of the hole in the tubesheet, tack rolled and then welded in place.

While space to maneuver is not a particular problem on the secondary side of the steam generator, the radius of the partitioned, hemispherical primary side is typically approximately five feet which does not provide much working room especially near the circumference of the

30 tubesheet. In addition, the primary side is radioactive

1122309 -4- W.E. 47,863

which requires worker protection and limitation of exposure time .

In an initial attempt to at least partially automate refurbishing of steam generators, a tool fixture was developed which cam locked into holes in the tubesheet to support a tool with an automatic feed. Only the drilling and spot-facing operation and the welding were performed by this unit and a worker was required to enter the confined primary side of the generator to move the fixture from one

10 hole set to the next. In view of the thousands of holes in the typical tubesheet, this procedure was very time consuming.

Subsequently, a fixture was developed which can be "walked" from hole to hole by an operator outside the steam generator. In this machine, the operator manipulates a scale model to move the cam locks from one hole to another by reference to a television screen. While this machine speeds up the drilling/spot-facing operation and the welding and reduces worker exposure to radioactivity,

20 it requires a skilled operator, still takes longer than desirable and does not perform all of the required operations so that a workman must still spend a considerable amount of time in the primary side of the generator. In addition, with both of these prior art fixtures the tube holes are spot-faced to a depth which is referenced to the face of the tubesheet adjacent the hole and not to a common plane.

It is a primary object of this invention to provide a method and apparatus which automates all the

30 retubing operations to minimize downtime and worker

1122309 -5- W.E. 47,863

exposure to radiation. It is another object of this invention to provide

such a method and apparatus which accommodates for the imprecise location of tube holes and provides a map of the exact locations.

It is yet another object of this invention to provide such a method and apparatus which accommodates for imperfections in the flatness of the tubesheet surface.

It is a more specific objective of the invention 10 to provide a method and apparatus such as in the previous

object for spot-facing the tube holes to a common plane despite imperfections in flatness of the tubesheet.

It is still another object of the invention to provide a method and apparatus which coordinates retubing operations on both the inlet and outlet sections of the steam generator primary side.

It is also an object of this invention to provide a method and apparatus for precise alignment of the apparatus with the tubesheet, taking into account imprecise

20 orientation of the tubesheet in the steam generator. Summary of the Invention

According to the invention, a steam generator is serviced by mapping the tubesheet with a probe to precisely locate each hole in the sheet and storing each such precise location. The stored locations are then used to maneuver various tools into position to perform one or more operations at each tube hole. These operations may include drilling out old tubes and spot-facing the drilled out holes, preferably to a common plane; inserting new tubes in

30 the holes and aligning the ends thereof flush with the

112:2309 -6- W.E. 47,863

spot-face; cleaning the tubesheet and tube end with a wire

brush; securing the tube ends in place, first by expanding

the tubes and then by welding; and then brushing and

remotely inspecting the welds.

The mapping is performed by maneuvering a probe

responsive to the walls of the holes in the tubesheet into

approximate alignment with a hole, advancing the probe into

the hole, maneuvering it until it is centered in the hole

and then recording the hole location. In the preferred

10 embodiment of the invention, the angular position of an arm

mounted for rotation parallel to the tubesheet and the

position of a carriage movable along the arm are adjusted

to align the probe with the holes. After the precise

location of a hole is stored, the arm and carriage

positions are adjusted to advance the probe a first preset

distance in a direction parallel to the row to generally

align the probe with the next hole to be probed and the

probe is advanced in this manner down the row. The probe is

then maneuvered a second preset distance in a direction

20 parallel to the columns and the same procedure is repeated

to precisely locate selected holes in another row. Thus,

rather than accumulating errors, the probe is maneuvered to

the general location of a hole by advancing it the preset

distance from the precise location of the previous probed

hole in the array.

When the first and second preset distances are

equal to the nominal distances between columns and rows

respectively, each hole in the array is probed. On the

other hand, when these preset distances are equal to

30 multiples of the nominal row and column spacing, only a

1122309 -7- W.E. 47,863

portion of the holes are probed and the locations of the other holes are determined by appropriately adding or subtracting the nominal row and column spacings to the measured coordinates of the nearest probed hole.

In order to assure precise alignment of the elongated arm parallel to the tubesheet before mapping, electrical signals representative of the distance from the free end of the arm to the tubesheet at three angular positions are generated and the pivot axis of the arm is

10 adjusted relative to the tubesheet until the three electrical signals are brought within a preset tolerance of being equal. With the arm pivoted about a point located near the center of the straight side of one semicircular half of the tubesheet, the flatness of the tubesheet can be determined by generating a fourth electrical signal representative of the distance from the arm to the tubesheet at a point near the pivot point of the arm and comparing it with the other signals. The resulting signal is then used in guiding a drill to spot-face all of the

20 holes to a common plane regardless of irregularities in the surface of the tubesheet.

The invention is also directed to coordination of the operation of pivoted tool supporting arms on opposite sides of the steam generator primary side divider plate. Operation of the two arms is coordinated to spot-face the holes on both halves of the tubesheet to a single common plane and to position the tools at preselected corresponding holes on the two sides of the divider plate. After the two ends of a U-shaped tube are inserted in the

30 corresponding holes, tools carried by the two arms

1122309 -8- W.E. 47,863

determine the distance that each end of the tube protrudes through the tubesheet . The tool arm servicing the end protruding the shortest distance is operated to position that end of the tube flush with the spot-face and to expand the tube to thereby secure it in place. Then the second tool is operated to similarly align and expand the other end of the tube, and both ends are automatically welded in place. Operation of the tools carried by the two pivoted arms is coordinated in this manner at successive pairs of

10 corresponding holes on opposite sides of the divider plate until all the tubes have been installed.

Use of the invention greatly decreases the time required to service a steam generator tubesheet and the exposure of workers to radioactivity. It also provides a precise map of the tubesheet which can be used for future reference.

Brief Description of the Drawings Figure 1 is a vertical section view taken along

the line I-I in Figure 2 with some parts removed for 20 clarity showing apparatus according to the invention in

place in a steam generator; Figure 2 is a bottom view of the steam generator

of Figure 1 ; Figure 3 is a plan view illustrating the array of

holes in the tubesheet of the steam generator of Figures 1 and 2;

Figure 4 is a vertical section through part of the tubesheet illustrating an exaggerated concave tubesheet surface ;

30 Figure 5 is a side elevation view of a servicing

i

1122309 -9- W.E. 47,863

machine according to the invention shown in place in one-half of the channel head of the steam generator of Figure 1;

Figure 6 is an enlarged longitudinal vertical section through the carriage mounted on the servicing machine of Figure 5;

Figure 7 is a plan view of the carriage; Figure 8 is a schematic diagram in block diagram

form of a control system in accordance with the invention; 10 Figure 9 is a block diagram illustrating in more

detail the control system for one axis of the system shown in Figure 8;

Figure 10 is a side elevation view of a probe suitable for use with the invention;

Figure 11 is a horizontal section through the probe of Figure 10 schematically showing sensor orientation ;

Figure 12 is an enlarged plan view of a portion of the tubesheet hole array shown in Figure 3;

20 Figure 13 is a flow chart schematically depicting the steps performed by the system in setting up the servicing machine;

Figure 14 is a flow chart schematically depicting the mapping operation;

Figure 15 is a flow chart schematically depicting the steps performed by the system in coordinating the operation of two servicing machines during retubing of a steam generator; and

Figure 16 is a flow chart schematically depicting 30 the steps performed by the system in sequentially

1JL22309 -10- W.E. 47,863

performing general operations at each hole in the tubesheet

array.

Description of the Preferred Embodiment

General Description

The invention will be described as applied to

servicing the steam generator 1 shown in Figure 1 for a

boiling water nuclear reactor electric power generating

system but it will become readily apparent that it can be

applied to servicing other types of steam generator

10 equipment. The system used in carrying out the invention

includes two remotely controlled servicing machines 3, one

of which is shown in detail in Figures 5 through 7. These

machines are adapted to receive a number of tools for

performing various functions within the steam generator and

are operated by the control system which is illustrated

schematically in Figures 8 and 9. The various tools include

a probe for aligning the machine during setup and for

mapping the precise location of each hole in the steam

generator tubesheet, a drill and spot-facing tool for

20 drilling out old tubes including plugged tubes and for

simultaneously spot-facing the drilled out holes, and

brushes for cleaning out the holes. Other tools used during

the retubing process include an extractor which removes

guides used to insert tubes through the tubesheet, an

expander which positions the newly installed tubes flush

with the tubesheet and expands them to bind them in place,

a wire brush tool used to clean the weld area before and

after welding, and a welding tool which automatically welds

the expanded tubes. Finally, a closed circuit television

30 camera is used to inspect the tube installation.

1 1 2 5 2 3 Q 9

-11- W.E. 47,863 The Steam Generator

Referring to Figure 1, the steam generator 1

comprises a cylindrical body portion 5 which is fitted at

its lower end with a hemispherical, shell 7. A transverse

steel plate 9, called a tubesheet, at the lower end of the

cylindrical portion divides the steam generator into a

primary side 11 below the tubesheet and a secondary side 13

above. The primary side 11, which is also referred to as

the channel head, is divided in half by a vertical divider

plate 15 into an inlet section 17 and a outlet section 19.

The tubesheet 9 is provided with an array of

thousands of holes 21, as shown in the plan view of

one-half of the tubesheet illustrated in Figure 3. Several

thousand U-shaped tubes 23 (only part of two of which are

shown in Figure 1 for clarity) are inserted into

corresponding holes 21 on opposite sides of the tubesheet

so that one end of each tube 23 communicates with the inlet

section 17 of the channel head and the other end

communicates with the outlet section 19. The tubes 21 are

supported on the secondary side 13 of the generator by a

series of separator plates 25 braced by tie rods 27 and by

antivibration bars 29.

Primary coolant from the reactor enters the inlet

side 17 of the channel head through inlet 31 (see Figure

2), circulates through the U-shaped tubes 23 and exits the

outlet side 19 of the channel head through outlet 33.

Secondary water introduced into the secondary side 13 of

the generator 1 through secondary water inlet 35,

circulates around the tubes 23 where it is converted to

steam by heat released by the primary coolant. Baffles 37

1122309 -12- W.E. 47,863

form a preheater section which initially directs the

secondary water around the inlet side of the tubes 23 for

increased efficiency. The steam produced in the secondary

side 13 rises into a steam drum (not shown) where water

droplets are removed by demisters and passes out of the

generator through a secondary outlet (not shown). T-shaped

blowdown tubes 39, one on each side of secondary side 13 of

the generator above the tubesheet 9 (only one shown in

Figure 1), are used to periodically inject pressurized

fluid around the exterior of the tubes 23 to remove

accumulated scale and residue.

Manways 41 and 43 provide access to the inlet

side 17 and outlet side 19 of the channel head 11 for

servicing. As shown in Figure 1, apparatus 3 for servicing

the tubes 23 and tube sheet 9 is inserted through the

manways 41 and 43 and setup in the channel head on each

side of the divider plate 15.

A typical array of holes 21 in a tubesheet 9 is

illustrated in Figure 3. As can be seen from the drawing,

the holes in each half of the tubesheet 9 are arranged in

rows which run horizontally in the figure and columns which

are oriented vertically to form a basically semi-circular

pattern. Certain holes in the array are missing such as

those that would fall in the T-shaped area 45 below the

blowdown tubes 39 and those that are replaced by the tie

rods 27. Otherwise, the entire area within the

semi-circular pattern is perforated with holes 21 although

only the peripheral holes have been shown for clarity.

The tubesheet 9 is a large steel plate which

typically may be more than ten feet in diameter and close

1122309 -13- W.E. 47,863

to two feet thick. The lower face 10 of the tubesheet is machined for flatness but, as a result of manufacturing tolerances, it is possible that this face 10 may be slightly concave or convex as illustrated in exaggerated form in Figure 4. The amount of deviation from the flatness of the lower tubesheet surface is determined during the setup operation as discussed below. Servicing Machine

A complete description of the servicing machine 3 10 is provided in commonly owned Canadian Patent No. 1,090,991

issued on December 9, 1980 referred to above. An apprecia-tion of the construction of the machines sufficient for the purpose of understanding the present invention can be gained by reference to Figures 5 through 7 where it can be seen that a vertical column 47 is mounted in the channel head 11 adjacent the divider plate 15 and generally perpendicular to the tubesheet 9. The lower end of the column 47 is pivotally supported by a spherical bearing unit 49 welded to the shell 7. A second support means 51, fastened to the

20 divider plate 15 by welding or other means, supports the upper end of the column 47. The column 47 is rotatably disposed within the second support means 51 by an anti-friction bearing such as a ball or roller bearing (not shown). The second support means 51 also has a split collar 53 disposed thereon with a gap 55 which is closed by a hydraulic cylinder 57 to lock the column 47 in any of its rotated positions.

The second support means 51 provides for 30 adjustments of the upper end of the column 47 in two

orthogonal directions in a plane parallel to the tubesheet

1,122303 -14- W.E. 47,863

9. Bolt 59 allows for the upper end of column 47 to pivot

to the right and left about the spherical bearing support

49 in the plane of Figure 5 while a dovetail and screw

arrangement 61 permits movement of the upper end of column

47 in a direction perpendicular to the plane of the figure.

An arm 63 is pivotally connected to the upper end

of column 47 by a suitable mounting bracket 65. The pivotal

connection is such that the arm 63 rotates with the column

47 but can be pivoted from a position generally parallel to

10 the tubesheet 9, as shown in Figure 5, to a position

wherein the free end of the arm is aligned with the manway

41. The arm is pivoted in this manner by a pair of

hydraulic cylinders 67 (only one shown in Figure 5)

pivotally connected to the lower end of column 47 by a

suitable bracket 69 and to the free end of the arm 63 by

another bracket 71.

A reversible hollow shaft DC motor 73 mounted on

the column 47 with a torque connection 75 to the divider

plate 15 rotates the column 47 to pivot the arm 63 in a

20 plane parallel to the tubesheet 9. The motor is provided

with means for precisely indicating the angular position of

the hollow shaft and therefore the arm 63.

The arm 63 comprises a pair of generally parallel

rails or channels 77 (only one shown in Figure 5) with ways

79 on the top and bottom portions of each channel 77. The

ways 79 extend longitudinally along the arm and are

parallel to each other. A carriage 81 slidably mounted on

the ways 79 has pairs of bearings 83 which engage each of

the ways 79 so that the carriage moves rectilinearly and

30 parallel to the longitudinal axis of the arm 63.

112:2309 -15- W.E. 47,863

The carriage 81, as shown best in Figures 6 and

7, comprises a baseplate 85 and a platform 87 disposed

generally parallel to each other and generally parallel to

the tubesheet 9 when the longitudinal axis of the arm 63 is

parallel thereto. The baseplate 85 is connected to the

bearings 83 and the platform 87 is disposed above and

parallel to the baseplate 85. An air motor 89 or other

suitable means for supplying a rotational drive force for

various tools is connected to the platform 87.

10 Means for raising and lowering the platform 87

with respect to the baseplate 85 and for maintaining

parallelism therebetween comprises four cylindrical posts

91, which are affixed adjacent the four corners of the

platform 87, eight ball bushings 93 disposed in the base

plate 85 for slidably receiving the posts 91, and a pair of

double acting hydraulic cylinders 95 connected to the

baseplate 85 and the platform 87. Means for indicating the

speed and position of the platform 87 with respect to the

baseplate 85 is shown generally at 97.

20 A cantilevered tool holder 99 is fastened to the

platform 87 and coupled to the drive motor 89. The

cantilevered tool holder has a tool receptacle or chuck 101

on the distal end thereof for holding a tool, and a train

of gears or other drive means 103 connects the drive motor

89 to the tool chuck 101 providing power to drive the tool

105.

Referring back to Figure 5, a ball screw 107,

drive motor 109 and ball nut 111 are coopérât! vely

associated with the arm 63 and carriage 81 to provide means

30 for moving the carriage rectilinearly along the arm and for

1,122303 -16- W.E. 47,863

holding the carriage 81 at any position along the arm 63. The ball screw 107 extends the length of the arm 63 and is disposed generally parallel to the longitudinal axis thereof. The ball nut 111 is affixed to the carriage 81 and engages the threads on the screw 105. Resolvers 113 are provided for indicating the position of the carriage along the arm.

Disposed on the arm 63 are a pair of hydraulic cylinders 115 which have piston rods 117 that can be

10 extended outwardly to contact the wall of the shell 7 to steady the arm 63 when the tool 105 is performing an operation on the tubes 23 or tubesheet 9.

The cantilevered tool holder 97, as shown best in Figure 7, has arcuate plates 119 equally spaced on opposite sides of the axis of the drive motor 89. Lugs 121 clamp the arcuate plates 119 and tool holder 99 to the platform 87. Dowels and dowel holes (not shown) are provided in the arcuate plate and in the platform so that the cantilevered tool holder can be aligned with the axis of the arm as

20 shown in Figure 6, rotated 180°, or rotated to form selected acute angles with respect to the axis of the arm as shown in Figure 7. The varying positions of the tool holder and the short column 47 provide access to all of the tubes in one-half of the tubesheet and establish accurate positioning of the tool holder to allow remotely controlled repeated operation on any tube in that half of the tubesheet. The described tool holder is specifically adapted for holding the drilling tool and may also be used to support the probe or brush. Other tool holders, carrying

30 other tools, may also be mounted on the carriage 81. Tool

1,122303 -17- W.E. 47,863

changes are effected by aligning the free end of the arm 63

with the manway 41 as shown in the right side of Figure 1.

While the tool holder shown is manually rotated to the

desired position and locked in place, an automotic slewing

tool holder, such as that disclosed in commonly owned U.S.

patent application Serial No. 896,530 filed on April 14,

1978, may also be utilized.

A C-shaped stiffening bracket 123 is fastened to

the column 47 spanning the motor 73 in order to reduce the

10 deflection in the column 47.

The described servicing machine may be easily and

quickly installed inside the head of a steam generator and

with an assortment of tools can perform various operations

on all of the tubes in one-half of the tubesheet. The

apparatus so structured is rugged and reliable so that it

can operate within the close tolerances necessary to retube

a steam generator utilizing remote controls. To operate

remotely, the angular position of the arm and column must

be repeatable. Accurate angular positioning and indicating

20 the angular position of the column and the arm is provided

by the motor 73 and once the column and arm are positioned

in the desired angular position, the split collar 53 locks

the column 47 in that position.

The carriage 81 is positioned by rotating the

ball screw and the motor has a brake disposed therein to

maintain the screw in any desired position. The nut which

rides on the threads of the screw has a plurality of balls

which engage the threads. This combination minimizes any

backlash, allowing very accurate positioning of the

30 carriage. This combination is not subject to be backdriven

1122309 -18- W.E. 47,863

by the carriage, therefore, with the drive motor brake

engaged, the carriage remains in a fixed position.

The hydraulic cylinders which raise the arm 63

from a position aligned with the rnanway 41 to a position

where it is generally parallel to the tubesheet 9

preferably act against a stop, when in the latter position,

to increase the rigidity of the apparatus.

The System

Figure 8 illustrates schematically in block

10 diagram form the servicing system. The system is controlled

by a digital computer, such as a Westinghouse 2500 Model D,

with the following features: power failure detection and

protection, automatic restarting, bootstrap loader, real

time clock and a 64K 16 bit/word nonvolatile memory. An

operator's indicator panel 127 provides the operator with

visual indications of system performance and status. A

cathode ray tube (CRT) display unit 129, with an integral

alphanumeric keyboard and off-line editing features,

functions as the main man-machine interface permitting the

20 operator to input operating parameters, data and

instructions to the computer, to display and edit input

information, and to have the collected data or programmed

responses automatically displayed for visual inspection. A

hard copy printer 131 with an integral alphanumeric

keyboard functions as a hard copy data input/output device

with the keyboard used as a backup CRT data input device.

The computer is programmed through a paper tape reader 133

and two magnetic tape units 135 are used to input mass

data, such as the tube array for the generator being

30 serviced.

1122309 - 1 9 - W.E. 47,863

The computer 125, supported by its peripheral

equipment, functions as a m o n i t o r i n g and control element

for the system. The computer monitors all strategic system

parameters arid controls all of the tool operating functions

through a control processor 137. The control processor 137

provides absolute position control for three axes on the

servicing machine 3, including: the angular position of arm

63 (the © axis) through control of motor 73; the position

of the carriage 81 along the arm (the R axis) through

10 control of carriage drive motor 109; and for the vertical

position of the tool above the carriage (the Z axis)

through control of double-acting hydraulic cylinders 95.

The drive system is configured to be a high performance

closed loop servo control system with a high degree of

accuracy, speed response and positioning control.

The main element of each axis drive system is an

absolute position controller using a remote positive

feedback unit in a closed loop position control system, as

shown in Figure 9. The input data for each axis is entered

20 from the computer 125 through line 139 into the control

processor 137 which distributes the operational data to the

preselected axis processor 141 and enters the desired axis

position into the axis memory 143. The axis position

comparator 145 then determines the amount the drive motor

is to move and in which direction by comparing the desired

position with the actual position in position indicator

147. The output of the comparator 145 is applied to the

axis motor drive 149 which applies electric power of the

proper polarity and magnitude to the axis motor 151, e.g.

30 carriage drive motor 109. As the selected motor turns, the

1122309 -20- w.E. 47,863

position feedback unit 153 associated therewith (such as

resolver 113) reports back to the axis processor 141

through line 155. When the desired and actual positions are

equal, the motor drive stops. As shown in Figure 8, the

control processor 137 reports back axis movement to the

computer over line 139. During drilling operations, the

drill bit speed is fed back directly to the computer 125

over line 157 so that the drill bit feed rate may be

ad justed to accommodate for changes in drill speed due to

10 variations in hardness of the drilled material, drill bit

wear, etc.

While each axis of the control processor 137

functions in the same manner to generate control signals

for the associated drive element on the servicing machine

3, the Z axis signal is applied to two hydraulic servos 159

which regulate the flow of hydraulic fluid from a hydraulic

system 161 to the two double-acting hydraulic cylinders 95

which raise and lower the platform 87 carrying the tool

holder 99. A level adjustment 163 can be used to set the

20 hydraulic servos 159 for leveling the platform 87.

The above described closed loop control system is

used in positioning and controlling the tools in all of the

following operations: setup, mapping, drilling/spot-facing,

tube guide removal, wire brushing, tube positioning/ex-

panding, welding and weld inspection. While the positioning

of the welding tool is controlled in the computer 125, the

welding parameters are automatically regulated by the

welding power supply 165. Upon completion of the welding

cycle, the power supply 165 notifies the computer which

30 positions the tool at the next hole and sends another start

X Ï 2 S 3 0 9

-21- W.E. 47,863

signal to the welding power supply.

The computer 125 controls and monitors the

operation of the two servicing machines 3 through similar

control processors 137. It also coordinates operation of

the two servicing machines during retubing as discussed

below.

The Tools

Various tools or end effectors may be used with

the servicing machine. These tools include a probe 165,

10 such as that shown in Figures 10 and 11, having an

elongated body portion 167 which may be inserted into the

holes 21 in the tubesheet. Orthogonally disposed pairs of

sensor coils 169 and 171 are mounted in the side walls of

the probe 165. Each pair of coils forms an eddy current

promixity detector which generates a null signal when the

probe is located equidistant from the axis of that coil

pair to the walls of the hole in which the probe is

inserted. With the probe 165 mounted in the tool holder 99

with the axis of coils 169 parallel to the axis of movement

20 of the carriage 81 (the R axis) and the axis of coils 171

parallel to the tangent to the rotational movement of the

boom 63 (the 6 axis), the signals generated by the sensors

can be used in the drive system of the servicing machine as

discussed below to precisely locate the centers of the

holes 21. The probe 21 is also provided with an end

proximity sensor 173 which, as discussed below, can be used

to determine the presence or absence of a hole at a

particular location and the distance between the servicing

machine carriage and the tubesheet 9 (the Z axis component)

30 for the purposes discussed below. Suitable probes of the

11Z2303

-22- W.E. 47,863 type described or others are available on the market. As an alternative, the end proximity detector can. be replaced by a limit switch to determine the Z axis component.

Another tool used by the servicing machine is a drilling and spot-facing tool. This tool, which is driven by the motor 89 through the gear train drive 103, is used to drill out plugged holes and old tubes. The drill bit is provided with a shoulder which spot-faces the drilled out holes as at 175 in Figure 4. Another tool adapted for use

10 with servicing machines is a brush which may be inserted into the tube for cleaning prior to retubing. A surface brush may also be used following tube alignment for preparing the surfaces for welding and for weld cleaning before inspection.

Since, as esqplained below, guides are inserted into the ends of the replacement U-shaped tubes 23 to guide them through the separator plates and the tubesheet 9, another tool is utilized to extract these guides following tube insertion. A suitable tool for this purpose is

20 described in the commonly owned Canadian patent application Serial No. 338,797 filed on October 31, 1979.

A tube expander tool is also used with the machine to expand the newly Installed tubes in the holes 21 to seal the holes and secure the tubes in place for welding. Tools of this sort are available on the market. A hydraulic tube expander particularly suitable for this purpose is de-scribed in commonly owned Canadian Patent No. 1,063,065 issued on September 25, 1979. Roller type tube expanders may also be used, such as that shown in U.S. patent 2,835,307.

1 1 2 2 3 0 3 -23- W.E. 47,863

Welding tools which automatically weld around tube ends are available on the market and can be controlled by the servicing machine. Finally, a closed circuit TV camera may be mounted on the carriage for inspecting the finished welds.

The probe, the drill and the brushes may be mounted on the tool holder shown and described in connection with Figures 6 and 7. The other tools which either have their own drive unit built in or do not require drive power,

10 such as the closed circuit TV camera, may be mounted on a tool arm without the gear train drive shown in Figure 7.

For changing the various tools, the arm 63 is rotated and the hydraulic cylinders 67 are operated to align the outwardly extended carriage 81 with the manway 41, as seen in the right side of Figure 1. In this manner, the tools can be quickly changed with minimum worker ex-posure to radiation in the channel head. Operations

In general terms, servicing machines 3 are set up 20 in both sides of the steam generator channel head 11 and

the parallelism of the arms 63 and the depth of the spot-face plane are determined as described below. The remaining functions performed by the servicing machines 3 can roughly be classified as detubing and retubing operations.

Detubing includes mapping the tubesheet 9 in the manner described below to determine the precise location of each hole in the array. It also includes drilling out the

1122309 - 2 4 - W . E . 4 7 , 8 6 3

holes and spot-facing them as also described below. Retubing includes inserting the ends of U-shaped

tubes in corresponding tubesheet holes communicating with the inlet and outlet side of the channel head respectively and extracting the guides used to drive the tube ends through the separator plates and the tubesheet. The ends of the tubes are then aligned flush with the spot-face surface adjacent each hole and secured in place by a tube expander. The tube ends are then welded in place and, following

10 brushing, the welds are remotely inspected by closed circuit TV.

A. Setup The first step in servicing the steam generator

is to set up the servicing machine 3 in the channel head 11 of the steam generator with the plane of rotation of the arm 63 parallel to the bottom face of the tubesheet 9. The machine is initially setup manually with the arm as parallel to the tubesheet face as can be determined by the worker.

20 For bringing the arm into precise alignment parallel to the tubesheet, the distance between the arm 63 and the tubesheet 9 is determined automatically by the system at three widely separated points referred to as parallel points A, B and C. In order to achieve better accuracy in establishing the plane of the tubesheet, the parallel points A, B and C are located near the periphery of the hole array and at the 0°, 90° and 180° points

1122309 -25- W.E. 47,863

respectively as shown in Figure 3. When these measurements,

which are taken in the form of electrical signals generated

by the probe, are within a predetermined tolerance of each

other (e.g. 0.001 inch), the arm may be considered parallel

to the tubesheet and the system can be advanced to the next

operation. In view of the high accuracy required for the

alignment, four measurements are taken at each location A,

B, and C to generate an average value. As seen in Figure

12, the four measurements used at location A are taken at

10 data points A^ through A^ in the land areas surrounding the

hole A which is at the center of the location. Four

similarly spaced measurements are also taken at data points

surrounding location B although there is no hole located

there. If the difference between the average measurements

taken at parallel points A, B and C is not within the

preset tolerance, the alignment of the support column 47 is

adjusted as described above and the measurements are

repeated until parallelism is achieved.

The procedure is described schematically in the

20 flow chart of Figure 13. As indicated in block 177, the

data of the first parallel point is entered and the arm 63

and the carriage 81 are positioned angularly and

longitudinally respectively as in block 179 to align the

probe 165 mounted on the carriage under the first data

point. The probe is then driven up as indicated in block

181 until the proximity end probe generates a preset signal

indicative of a preset distance from the tubesheet or the

limit switch is activated. The elevation of the probe,

which is indicative of the distance between the arm and the

30 face of the tubesheet, is recorded as in block 183 and then

1122309 -26- W.E. 47,863

the probe is lowered for repositioning as in block 185. If

this is not the last of the four points around the selected

location A, B and C as determined in block 187, the

coordinates of the next data point, are entered as in block

189 and the previous steps are repeated. When the

measurements at all four data points have been completed,

the average measurement for that parallel point is

determined in block 191. If this is not the last of the

three locations A, B and C as determined in block 193, the

10 data of the next parallel point is entered as indicated in

block 195 and the average distance for each location is

determined as above. The average distances for the parallel

points A, B and C are then compared in block 197 to

determine if the arm is parallel to the tubesheet. If the

average distances are not within the preset tolerances,

such as ± 0.001 inches, as determined in block 199, an

operator alarm is generated and the average distances are

printed out, block 201. The system then waits for a restart

command, block 203, while the alignment of the support

20 column 47 is adjusted as described above based upon the

printed results. After realignment, the operator initiates

a restart which reenters the data for the first parallel

point at block 205 and the entire above described sequence

for checking parallelism of the arm 63 and tubesheet 9 is

repeated.

When it is determined in block 199 that the

distance to the three parallel points is within the preset

tolerance and therefore the arm is parallel to the

tubesheet, the flatness of the tubesheet is determined in

30 block 107. Since the known deviations from flatness for the

112:2309 -27- W.E. 47,863

Lubesheet are either a concave or convex face, only one

additional reading as at point D (see Figure 3) near the

center of the tubesheet need be taken. This is accomplished

by retracting the carriage 81 carrying the probe to a point

near the pivoted end of arm 63, taking four measurements of

the distance to the tubesheet around the location D and

averaging them as in the cases of points A through C. If

the distance between the arm and the tubesheet at point I)

is greater than the distances at A through C, then the

10 tubesheet is concave, whereas it is convex if point D is

closer to the arm than the other points. In any event, the

determination of the spot-face plane location is made in

block 109 by adding a preset tolerance to the greater of

the distances of the parallel points A, B or C or the point

D from the arm, and this Z axis information is stored and

printed out as in block 211. Preferably, the parallel point

and D point readings for both sides of the tubesheet are

compared and a common spot-face plane is established across

the tubesheet.

20 B. Mapping

The probe 165 is also used in mapping the holes

in the tubesheet to determine the precise location of each

of the thousands of holes which may be arranged in a

pattern, such as that illustrated in Figure 3. By way of

example, the holes in the tubesheet may be 0.762 to 0.767

inches in diameter with the rows and columns spaced on

1.0625 inch centers. While the tubesheets are carefully

machined during manufacture, it is desirable during

servicing of the steam generator to determine the location

30 of the holes to the nearest 0.001 inch.

1122309 -28- W.E. 47,863

The mapping procedure is set forth schematically

in the flow chart of Figure 14. The R and 6 drives which

respectively control the angular position of the arm 63 and

the longitudinal position of the carriage 81 are actuated

to position the probe 165 under the best known position of

the hole at row 1, column 1 as entered by the operator. The

Z axis drive which controls the vertical movement of the

platform 87 on the carriage 81 is then activated to insert

the probe into the hole as indicated in block 213. If the

10 probe is not centered as indicated by the absence of a null

on the 9 or R axes sensors, block 215, the 9 or R axis

drives are actuated to null the respective sensors as

indicated at blocks 217 and 219. Since adjustment of the

null position on ohe axis may affect that of the other

axis, the probe centered check is made again in block 215

after each adjustment until the precise center of the hole

is located. The actual location of the hole to the nearest

0.001 inch is then stored as in block 221.

If this is not the last hole in the row as

20 determined in block 223, a preset distance equal to the

nominal distance between columns, in the example 1.0625

inches, is added to the column coordinate and the probe is

advanced to the resultant position as in block 225. The end

sensor on the probe is then utilized to determined whether

this new hole is plugged or missing as in block 227. If it

is plugged, this fact is recorded and the probe is advanced

to the next hole in the row by returning to block 223. If

this new hole is not plugged or missing, the probe is

inserted into the hole as in block 229 to a depth suitable

30 for operation of the R and Q sensors and the precise

1122309 -29- W.E. 47,863

location of the hole is determined and recorded as

previously described.

When the precise location of the last hole in the

row has been determined as in block 223, and it is not in

the last row, block 231, the nominal distance between rows,

again by way of example, 1.0625 inches is added to the row

coordinate to align the probe with the next row as in block

233. Since the rows do not have an equal number of holes

due to the shape of the hole array, the column coordinate

is adjusted in block 235 for each new row to position the

probe at the first hole in that row. The test is then made

again for a plugged or missing hole as in block 227 and the

mapping of the row continues as previously described.

When all of the holes in all of the columns have

been similarly mapped as determined in block 231, a review

is made of unmapped i.e. plugged holes in block 237 . If

there were no plugged holes, mapping is completed. If there

were plugged holes, their location is calculated and stored

in block 239 by applying the nominal distances between rows

and columns to the location of holes adjacent the plugged

holes. When the location of all of the plugged holes has

been calculated, as determined in block 241, the mapping

operation is completed.

The precise location of each hole in the array

and whether or not it is plugged is stored by the system

for use in performing further operations at each hole

location and may be printed out to provide a precise map of

the tubesheet array.

It has been found that for large sections of the

tubesheet hole array, the location of each hole can be

1122309 -30- W.E. 47,863

determined within satisfactory tolerances without inserting

the probe into each and every hole. Instead, the probe may

be inserted in every third or fifth hole, for example, with

the location of the skipped holes being calculated by

adding the nominal distance between holes to the

coordinates of the closest probed hole. For instance, if

the probe is only inserted in every fifth hole in a row,

the location of the second hole is determined by adding the

nominal distance between holes, in the example 1.0625

10 inches, to the column coordinate of the first hole. Twice

this distance, or 2.125, is added to the first hole column

coordinate to determine the location of the third hole.

Similarly, the locations of the fourth and fifth holes are

determined by subtracting 2.125 and 1.0625 inches

respectively from the column coordinates of the sixth hole

after it has been probed. The row coordinate is made equal

to that of the hole used in determining the column

coordinate.

In like manner, rows may be skipped as well as

20 columns so that only holes in every third or fifth row, for

example, are probed with the locations of the skipped holes

being determined by calculation from the nearest probed

holes. As an illustration, if only holes in every third row

and column are probed, such as the center hole A in Figure

12, the locations of the six holes surrounding hole A can

be calculated by adding or subtracting the nominal

distances on rows and columns to the measured coordinates

of hole A. It can be appreciated that the locations of the

six holes surrounding each probed hole can be determined in

30 a similar manner.

112:2309 -31- W.E. 47,863

As applied to the flow chart of Figure 14, the

preset distance that the probe is advanced along the row as

indicated in block 225 will be equal to the distance

between probed holes or, for example, three or five times

the nominal distance between holes where only every third

or fifth hole is probed. If the hole selected for probing

is plugged or missing, the preset distance added in block

225 the next time may be equal to plus or minus the nominal

distance between holes so that either the next hole or the

10 previous hole is substituted for the plugged or missing

hole. When the preselected number of holes in the row have

been probed, the probe is advanced the preset distance

along the columns block 233, again for example three or

five times the nominal distance between rows, to align the

probe with the next selected row.

After probing is completed as indicated in block

231 and it is determined in block 237 that there are

unmapped holes which, of course, there will be if holes

have been skipped, the location of the skipped holes and

20 unplugged holes, if the probe found any, are calculated in

block 239 in the manner explained above. When all the

unmapped holes have been located as determined in block

241, mapping is completed.

C. Drilling and Spot-Facing

Once a map of the precise location of each hole

in the tubesheet has been made, the drilling and

spot-facing tool is inserted in the tool holder 99 and the

holes are drilled out to remove the ends of the old tubes

and any plugs. As explained above, the drill is provided

30 with a shoulder which spot-faces the drilled out holes. The

1 1 2 2 3 0 9 -32- W.E. 47,863

depth of drilling is controlled by the system such that all of the holes 21 are spot-faced as shown at 175 in Figure 4 to the common plane established during the setup operation described above regardless of any curvature of the tubesheet lower face 10. As also mentioned previously, the computer monitors drill speed and adjusts the drill feed rate to accommodate for variations in material hardness.

D. Retubing The U-shaped tubes 23 are inserted in the

10 tubesheet 9 from the secondary side with the ends of the tube in corresponding holes on opposite sides of the divider plate 15. The tubes are inserted so that both ends extend one-quarter to one-eighth inch below the spot-face surface adjacent the corresponding holes 21. The operation of the two servicing machines 3, one on each side of the divider plate 15 in the channel head 11, is then coordinated to position and secure the tubes with their ends flush with the spot-face surface.

A flow chart schematically illustrating the 20 procedure is shown in Figure 15. The positioning data for

the first pair of corresponding holes is entered into each servicing machine 3 at block 243. The left and right servicing machines are then positioned with the tool holder aligned with appropriate corresponding holes as in blocks 245 and 247 respectively. The Z axis of the two machines are then driven up as in blocks 249 and 251 to detect the end of the tube extending downward through the tubesheet. This may be effected with a limit switch carried by the tool holder and as disclosed in the commonly owned Canadian

30 Application Serial No. 336,549

1 1 2 2 3 0 9 -33- W.E. 47,863

this limit switch can be mounted on a tube expander tool.

The distance that each tube protrudes below the face of the

tubesheet is then determined in blocks 253 and 255 using

the distances measured during the setup operation. These

two tube end to tubesheet distances are then compared in

block 257 to determine which tube end is closer to the

tubesheet. If the right side is closest, as determined in

block 259, the platform holding the expander tool on the

right side servicing machine is raised to align the end of

10 the right side tube flush with the spot-face 175 as indicated

in block 261. The tube end is then expanded by the expander

tool as in block 263 to secure the tube end in place for

subsequent welding and the fact that this step has been

performed is recorded in block 265. If the other tube end

has not yet been expanded as determined in block 267, the

left side tube end is aligned flush with the spot-face as

indicated at block 269, the tube is expanded as in block

271 and the data is recorded as in block 273. Since, in

this example, the other tube end has been expanded as de-

20 termined in block 275, the system will advance to block

277 to determine if all the tubes have been expanded. It

can be appreciated, however, by studying Figure 15 that

the tube end closest to the tubesheet will be aligned and

expanded first and then the other will be secured. This

is done to assure that the other tube end, which will tend

to ride up when the first end is pushed upward, will still

extend below the tubesheet and can be positioned by pushing

upward after the first end has been secured by expansion.

If it is determined in block 277 that there are

1122309 -34- W.E. 47,863

more tubes to be aligned and secured, the coordinates of

the next corresponding pairs of holes is determined in

block 279 and the above steps are repeated. The ends of

each of the thousands of tubes in the tubesheet are secured

in a similar manner. When the last tube has been secured as

determined in block 277, the results are printed out as in

block 279.

Other Operations

Following expansion of the tubes to secure them

10 for welding, the surfaces to be welded are cleaned by a

wire brush tool and welded. The welds are then inspected by

closed circuit television. Once the welding tool is

positioned by the servicing machine under the tube to be

welded, the tool operates automatically to direct the

welding arc in a circular path around the end of the tube.

Similarly, the tube guide extractor and tube expander also

operate automatically once they are positioned. Hence the

system only need position these tools sequentially at each

location where the specified operation is to be performed

20 and then initiate tool operation. This sequence is shown

schematically in the flow chart of Figure 16. As indicated

in block 281, the tool is positioned by the servicing

machine 3 at the first hole on which the operation is to be

performed. Tool operation is then initiated as in block 283

and, following completion of the operation, a determination

is made in block 285 if there are any more holes on which

the operation is to be performed. If so, the exact

coordinates of the next location as determined in the

mapping operation are entered as in block 287 and the

30 sequence is repeated until the operation has been performed

X1ZZ3QB -35- W.E. 47,863

at every hole. While it will be recalled from the

discussion above that the power supply for the welder may

be directly controlled by the welder, the welding tool

itself is controlled in the manner just described.

While the invention has herein been shown and

disclosed in what is conceived to be a practical and

effective embodiment, it is recognized that departures may

be made therefrom within the scope of the invention, which

is not to be limited to the details disclosed herein but is

to be accorded the full scope of the appended claims as to

embrace any and all equivalents.

i t z z s m

-36- W.E. 47,863 WE CLAIM:

1. A method of servicing a steam generator in which tubes are inserted in an array of holes in a tubesheet, said method comprising the steps of:

mapping the tubesheet by maneuvering a probe across the tubesheet to precisely locate each of said holes, generating a representation of each precise hole location and storing each of said representations; and

maneuvering a tool sequentially to the precise location of each hole in the tubesheet in response to said stored representations of said hole locations and controlling said tool to perform a preselected operation at each such hole location.

2. The method of claim 1 including the steps of changing the tool to a second tool, maneuvering said second tool sequentially to the precise stored location of each hole in the tubesheet in response to said stored represen-tations and operating said second tool to perform a second preselected operation at each such hole location.

1 1 2 2 3 0 9

-37- W.E. 47,863 3- The method of claim 1 wherein said preselected

operation is drilling out and spot-facing each hole. 4. The method of claim 3 including the steps of

positioning one end of a tube into a hole in the tubesheet and controlling a tool to secure said tube in place in the tubesheet.

5. The method of claim 4 including the step prior to securing the tube in place of controlling a tool to align the end of the tube flush with said spot-face.

6. The method of claim 4 wherein the step of securing the end of the tube in place includes the steps of controlling a tool to expand the tube in place in the tube-sheet and the step of controlling a welding tool to weld the tube end to the tubesheet.

7. The method of claim 1 wherein the step of mapping the precise location of the holes in the tubesheet compreises the steps of sequentially maneuvering a probe responsive to the proximity of the walls of the tubesheet holes to a position approximately aligned with the axis of selected holes, advancing the probe into said holes, maneuvering the probe in response to signals generated thereby until it is located in the center of said holes, generating representations of the locations of the probe at which it is so centered and storing such representations.

8. The method of claim 7 wherein said selected holes include substantially all the holes in the tubesheet.

9. The method of claim 7 wherein said selected holes include less than all said holes and the locations

1 1 2 2 3 0 9 -38- W.E. 47,863

of the holes which are not probed are determined by applying the nominal distances between rows and columns to the representations of the measured location of the probed holes and storing the resultant representations.

m

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1122303

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1122309

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153

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287

F i g . 16

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1122309

177-ENTER DATA OF FIRST PARALLEL POINT

181

POSITION PROBE TO TUBE SHEET DATA POINT

+ I

-179

DRIVE PROBE UP TO PRESET LIMIT

I RECORD 2 AXIS READING 183

185 POSITION PROBE IN DOWN POSITION

IS THIS THE LAST DATA POINT

191

187

DETERMINE PARALLEL POINT AVERAGE VALUE

193-

\N0 189

ENTER DATA OF NEXT DATA POINT

IS THIS THE LAST PARALLEL POINT

197-

YESj/

195

NO

199 207,

DET. PARALLELISM OF ARM TO TUBESHEET *

ENTER DATA OF NEXT PARALLEL POINT

\ V E S Z

IS ARM PARALLEL TO TUBE SHEET

N. NO DET. FLATNESS OF TUBE SHEET

OPERATOR ALARM PRINT RESULTS

.201

209 DET. DEPTH OF SPOTFACE PLANE

211—

X

WAIT FOR REENTER DATA OF RESTART FIRST PARALLEL POINT

STORE Z- AXIS DATA a PRINT RESULTS 205 7

205

Fig. 13

1 : 1 2 2 3 0 9 / J ? - / /

1122309

2 4 3 — E N T E R U'TUBE POSITIONING DATA INTO EACH SERVICING MACH.

POSITION LEFT MACHINE UNDER TUBE END

i :

-245 247-

DRIVE Z AXIS UP TO DETECT TUBE END

X -249

251-

POSITION RIGHT MACHINE UNDER TUBE END

4 : DRIVE Z AXIS UP TO DETECT TUBE END

DETERMINE TUBE END TO TUBESHEET DISTANCE

-253 255

X DETERMINE TUBE END TO TUBESHEET DISTANCE

257-

259

DETERMINE WHICH END IS CLOSER TO TUBESHEET

± IS RIGHT SIDE TUBE CLOSEST TO TUBESHEET

269n NO ! Z YES 261

POSITION LEFT SIDE TUBE INTO TUBESHEET

271-

273-

275-

EXPAND TUBE END

RECORD DATA

• t IS OTHER SIDE EXPANDED

Y ES/ \N0

POSITION RIGHT SIDE TUBE INTO TUBESHEET

263-

265-

267-

EXPAND TUBE END

RECORD DATA

IS OTHER SIDE EXPANDED

NO. .YES

YES/

IS LAST TUBE EXPANDED

PRINT RESULTS

-277

279

SELECT COORDINATE OF NEXT HOLE SET

F i g . 15